Tool with releasably mounted self-clamping cutting head

ABSTRACT

A metal cutting tool has a cutting head releasably mounted on a front end of a tool shank, in a self-clamping manner. The tool shank&#39;s forward end is provided with a pair of shank coupling portions, each having a forwardly facing shank support surface. A pocket recess is defined between the shank&#39;s coupling portions. Within the pocket recess are a plurality of shank fixation surfaces which are parallel to a longitudinal axis of the tool shank. The cutting head has a cap portion and a fixation portion extending in rearward direction therefrom. The cap portion includes a pair of head segments, each having a rearwardly facing head base surface. The cutting head&#39;s fixation portion has a plurality of head fixation surfaces which are parallel to a longitudinal axis of the cutting head. In the assembled tool, the tool shank&#39;s forwardly facing shank support surfaces support the cutting head&#39;s rearwardly facing head base surfaces, while the plurality of head fixation surfaces abut the plurality of shank fixation surfaces.

RELATED APPLICATIONS

This is a Continuation of U.S. patent application Ser. No. 12/016,449,filed Jan. 18, 2008, now U.S. Pat. No. 8,021,088. The contents of theaforementioned application are incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The current invention relates to a rotary cutting tool in general and,in one embodiment, to a drill having a releasably mounted cutting head.

BACKGROUND OF THE INVENTION

U.S. Published Patent Application No. 2005/0260046 A1 discloses acutting tool comprising a cutting head having a cutting headlongitudinal axis and tool shank having a shank longitudinal axis. Thecutting head includes a cap portion and a fixation portion connected tothe cap portion. The cap portion has a pair of head segments, eachhaving a rearwardly facing head base surface, and the fixation portionhas one or more sloped head fixation surfaces. The tool shank, at afront end thereof, has a pair of resilient shank coupling portionsseparated by a pair of shank flutes. The forwardly facing front ends ofeach shank coupling portion is provided with a shank support surfaceconfigured to support a corresponding head base surface. Inner surfacesof the shank coupling portions are provided with one or more shankfixation surfaces sloped with respect to the longitudinal axis of thetool. The sloped shank fixation surfaces are shaped and configured toabut the sloped head fixation surfaces of the cutting head. When thetool is assembled, the shank support surface supports the head basesurface and the one or more head fixation surfaces abut the one or moreshank fixation surfaces. After a drilling operation, when it is desiredto remove the cutting head from the recently-made hole, the bulbousfixation portion prevents the cutting head from slipping out of theshank coupling portion, as the tool is withdrawn from a workpiece.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a metal drillcutting head having a longitudinal axis (L) defining forward andrearward directions as shown in co-pending Israeli application number IL181296. The inventive metal cutting head includes a cap portion and afixation portion. The fixation portion is joined to the cap portion andextends in a rearward direction of the cutting head. The cap portioncomprises a plurality of head segments separated by at least first andsecond head flutes, each head segment comprising a rearwardly facinghead base surface formed at a rearward end of the cap portion. Thefixation portion comprises: a mounting stem connected to the capportion; a bulge formed on the mounting stem, the bulge comprising aplurality of circumferentially spaced apart protrusions, the protrusionsdefining a maximum dimension of the fixation portion in a directionperpendicular to the cutting head longitudinal axis; and a plurality ofspaced apart head fixation surfaces formed along the fixation portion,each head fixation surface being parallel to the cutting headlongitudinal axis.

In another aspect, the present invention is directed to a metal cuttingtool comprising a metal cutting head releasably mounted on a forward endof a tool shank, the metal cutting head and the tool shank having acommon axis of rotation and a common direction of rotation. The metalcutting head is of the sort summarized above. The tool shank comprises ashank longitudinal axis (S) which is coincident with the common axis ofrotation, and a plurality of shank coupling portions, equal in number tothe plurality of head segments, formed at the forward end of the toolshank, and a shank pocket recess formed between the shank couplingportions. Each shank coupling portion includes a forwardly facing shanksupport surface; and an inner surface comprising a plurality shankfixation surfaces, each shank fixation surface being parallel to theshank longitudinal axis. In the assembled metal cutting tool, therearwardly facing head base surface of each head segment is supported bythe forwardly facing shank support surface of a corresponding shankcoupling portion, each head fixation surface abuts an opposing shankfixation surface over an abutting region, and the entire bulge is spacedapart from walls of shank pocket recess.

In yet another aspect, the present invention is directed to a method forassembling a metal cutting tool comprising a cutting head having a capportion and a fixation portion provided with a bulge, and a tool shankhaving a pair of shank coupling portions defining a shank pocket recesstherebetween. The inventive method comprises: axially aligning thecutting head and the tool shank so that cutting head segments and shankflutes are arranged in opposing pairs; urging the cutting head and thetool shank towards each other so that the shank pocket recess receivesthe fixation portion; and rotating the cutting head relative to the toolshank until head fixation surfaces which are parallel to a longitudinalaxis of the cutting head abut shank fixation surfaces which are parallelto a longitudinal axis of the shank, such that the entire bulge isspaced apart from walls of the shank pocket recess; and a head torquetransmission wall abuts a shank torque transmission wall.

In still another aspect, the present invention is directed to a metalcutting head having a cutting head longitudinal axis (L) definingforward and rearward directions, the metal cutting head comprising: acap portion comprising at least one head segment, said at least one headsegment comprising a rearwardly facing head base surface formed at arearward end of the cap portion; and a fixation portion joined to thecap portion and extending in a rearward direction of the cutting head.The fixation portion comprises: a mounting stem connected to the capportion; a bulge formed on the mounting stem, the bulge comprising atleast one circumferentially extending protrusion defining a maximumdimension of the fixation portion in a direction perpendicular to thecutting head longitudinal axis; and a plurality of spaced apart headfixation surfaces formed along the fixation portion, each head fixationsurface being parallel to the cutting head longitudinal axis.

In still another aspect, the present invention is directed to a metalcutting tool having a metal cutting head releasably mounted on a forwardend of a tool shank, the metal cutting head and the tool shank having acommon axis of rotation and a common direction of rotation. The metalcutting head has a cutting head longitudinal axis (L) which iscoincident with the common axis of rotation and has at least two headfixation surfaces that comprise a portion of a circular cross sectionthat is perpendicular to the longitudinal axis (L). The tool shank has ashank longitudinal axis (S) which is coincident with the common axis ofrotation and has at least two shank fixation surfaces that comprise aportion of an elliptical cross section that is perpendicular to theshank longitudinal axis (S).

-   -   In yet another aspect of the present invention the metal cutting        head further comprises at least two head flutes and a tool shank        further comprises at least two shank flutes;        -   and in a fully mounted position the head flutes and the            shank flutes are generally aligned and there is a gap            adjacent the flutes between the head fixation surface and            the shank fixation surface

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how thesame may be carried out in practice, reference will now be made to theaccompanying drawings, in which:

FIG. 1 is view of a tool in accordance with one embodiment of thepresent invention;

FIG. 2 is a perspective view of a cutting head in accordance with oneembodiment of the present invention;

FIG. 2A is a perspective view of a cutting head in accordance with anembodiment of present invention in which no coolant channels areprovided;

FIG. 3 is a side view of the cutting head shown in FIG. 2;

FIG. 4 is a top view of the cutting head shown in FIG. 2;

FIG. 4A is a top view of the cutting head shown in FIG. 2A;

FIG. 5 is a bottom view of the cutting head shown in FIG. 2;

FIG. 5A is a bottom view of the cutting head shown in FIG. 2A;

FIG. 6 is a cross-section of the cutting head seen in FIG. 4 taken alonglines VI-VI;

FIG. 7 is a perspective view of the front end of a tool shank inaccordance with one embodiment of the present invention;

FIG. 7A is a perspective view of the front end of a tool shank inaccordance with an embodiment of present invention in which no coolantchannels are provided;

FIG. 8 is a partially exploded view of the cutting head of FIG. 2 andthe tool shank of FIG. 7;

FIG. 8A is a partially exploded view of the cutting head of FIG. 2A andthe tool shank of FIG. 7A;

FIG. 9 is a view of the cutting head of FIG. 2 almost fully mounted inthe tool shank of FIG. 7;

FIG. 9A is a view of the cutting head of FIG. 2A almost fully mounted inthe tool shank of FIG. 7A;

FIG. 10 is a view of the assembled tool including the cutting head ofFIG. 2 fully mounted in the tool shank of FIG. 7;

FIG. 11 is a cross-section of the tool seen in FIG. 10 taken along linesXI-XI;

FIG. 12 is a partial cross-sectional view of a tool in accordance with asecond embodiment of the present invention;

FIG. 13 is a partial cross-sectional view of a cutting head inaccordance with a third embodiment of the present invention;

FIG. 14 is a partial cross-sectional view of a cutting head inaccordance with a fourth embodiment of the present invention;

FIG. 15 is a partial cross-sectional view of a cutting head inaccordance with a fifth embodiment of the present invention;

FIG. 16 is a perspective view of a tool comprising a cutting head andshank in accordance with a sixth embodiment of the present invention;

FIG. 17 is a perspective view of the partially assembled tool shown inFIG. 16;

FIG. 18 is a side view of the assembled tool shown in FIG. 16;

FIG. 19A is a schematic cross section of the tool shown in FIG. 1wherein a fixation portion of a cutting head is inserted into toolshank;

FIG. 19B is a schematic cross section of the tool shown in FIG. 19Awherein the fixation portion of the cutting head is partially mounted inthe tool shank; and

FIG. 19C is a schematic cross section of the tool shown in FIG. 19Awherein the fixation portion of the cutting head is mounted in the toolshank.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The contents of aforementioned U.S. Published Patent Application No.2005/0260046 A1 are incorporated by reference to the extent necessary tounderstand the present invention.

FIG. 1 shows a tool 90 in the form of a drill in accordance with oneembodiment of the present invention. The drill 90 includes a cuttinghead 100 releasably mounted on a shank 200 with the cutting head and theshank having a common longitudinal tool axis X around which the toolrotates. The shank 200 is provided with at least two shank flutes 260A,260B, each of which connects to a corresponding head flute 138A, 138,respectively, formed on the cutting head 100. In one embodiment, theshank flutes 260A, 260B extend in a generally helical manner along aportion of the common longitudinal tool axis X. The cutting head 100 istypically made of hard wear resistant material such as cemented carbide,and the tool shank 200 is typically made of steel.

With reference to FIGS. 2-5, the cutting head 100 has a cutting headaxis L, an operative direction of rotation R, and comprises a capportion 118 and a fixation portion 120. The cap portion 118 comprises ahead top surface 122, a head base surface 124 transverse to the cuttinghead axis L and a peripheral side surface 126 extending therebetween.The fixation portion 120 protrudes rearwardly from the head base surface124 away from the head top surface 122. The fixation portion includes amounting stem 106 connected to the cap portion 118 and directed awaytherefrom, and a bulge 108 formed on the mounting stem 106. In theembodiment of FIGS. 2-6, the bulge is formed on a lower end of themounting stem 106. The bulge 108 bulges relative to the mounting stem106 in a direction generally transverse to the cutting head axis L andin particular in perpendicular to the cutting head axis L.

The bulge 108 has a rounded bottom 109 which merges into at least fourcircumferentially spaced apart protrusions, including a first pair ofprotrusions 110A, 110B, located on opposites sides of a first head flute138A and a second pair of protrusions 110C, 110D (see FIG. 5) located onopposite sides of the second head flute 138B. Alternatively, one mayregard one pair of protrusions 110A, 110D as being associated with afirst cutting head segment 140A and a second pair of protrusions 110B,110C as being associated with a second cutting head segment 140B (seeFIG. 5). Opposing pairs of the protrusions 110A, 110B, 110C, 110D definea maximum dimension W3 of the fixation portion 120 in a directionperpendicular to the cutting head longitudinal axis L (see FIG. 6).

At least four head fixation surfaces 128A, 128B, 128C, 128D are formedon the fixation portion. Each head fixation surface 128A, 128B, 128C,128D is parallel to the cutting head longitudinal axis L. Furthermore,as best seen in FIGS. 3 and 6, one pair of head fixation surfaces 128A,128D is associated with a first cutting head segment 140A, while asecond pair of head fixation surfaces 128B, 128C is associated with asecond cutting head segment 140B.

In some embodiments the four head fixation surfaces 128A, 128B, 128C,128D are formed along the mounting stem 120, each head fixation surface128A, 128B, 128C, 128D located between a corresponding protrusion 110A,110B, 110C, 110D, respectively, and the cap portion 118. Given thedirection of rotation R of the cutting head 100, head fixation surfaces128A, 128C may be referred to as the leading head fixation surfaceswhile head fixation surfaces 128B, 128D may be referred to as thetrailing head fixation surfaces. Similarly, protrusions 110A, 110C maybe referred to as the leading protrusions while protrusions 110B, 110Dmay be referred to as the trailing protrusions.

Since each head fixation surface is associated with a correspondingprotrusion, a first pair of head fixation surfaces 128A, 128B isseparated by the first head flute 138A, while a second pair of headfixation surfaces 128C, 128D is separated by the second head flute 138B.Adjacent head fixation surfaces that are between the first and secondhead flutes are separated by a head fixation recess 132A, 132B formed inthe mounting stem. For instance, head fixation surfaces 128B, 128C areseparated by head fixation recess 132A while head fixation surfaces128A, 128D are separated by head fixation recess 132B. In oneembodiment, each head fixation surface has an arcuate shape in across-section taken perpendicular to the cutting head longitudinal axisL and passing through the head fixation surfaces (see FIG. 11), and thuscomprises a portion of a cylindrical shell. As seen in the cross-sectionof FIG. 11, the head fixation surfaces 128A, 128B, 128C, 128D are theradially outermost surfaces and so no other surface extends outward ofthe head fixation surfaces in a radial direction.

Each head fixation surface is separated from its correspondingprotrusion by a notch 130A, 130B. As seen in FIGS. 2 and 3, headfixation surface 128A is separated from protrusion 110A by notch 130A;head fixation surface 128B is separated from protrusion 110B by notch130B, and head fixation surface 128C is separated from protrusion 110Cby notch 130C. As best seen in FIG. 6, each notch has deepest portionthat is radially inward of an adjacent head fixation surface.

As seen in FIGS. 2 and 3, in one embodiment, each protrusion (e.g.,110A, 110B) is provided with a beveled protrusion surface 133 whichforms an upper surface of the protrusion. The beveled protrusion surface133 extends from a radially inward position to a radially outwardposition, in a rearward direction of the cutting head 100. Eachprotrusion is further provided with a radially outwardly facingprotrusion surface 135 which forms a radially outermost surface of theprotrusion, and connects to the beveled protrusion surface 133. Theradially outwardly facing protrusion surface 135 is parallel to thecutting head longitudinal axis L. As seen in these figures, each beveledprotrusion surface 133 forms a lower portion of a corresponding notch.

Two head flutes 138A, 138B extend generally axially rearwardly along aperiphery of the cap portion 118 and fixation portion 120, forming twoidentical head segments 140A, 140B therebetween (FIG. 4). Each headsegment 140A, 140B comprises a cutting edge 142 formed along anintersection of an adjacent rake surface 143 with the head surface 122.Each cutting head segment 140A, 140B also comprises a cap recess 144(FIG. 5) which opens out to the peripheral side surface 126 and to thehead base surface 124. The cap recess 144 divides the head base surface124 into a first component head base surface 146 at a leading end of thecutting head segment 140A, 140B and a second component head base surface148 at a trailing end of the cutting head segment 140A, 140B.

In some embodiments, a head coolant channel 150 (FIGS. 4 & 5) opens outto the head surface 122, peripheral side surface 126, and secondcomponent head base surface 148 and intersects the cap recess 144. Ahead torque transmission wall 152 adjacent the first component head basesurface 146 extends along a portion of the cap recess 144 transverse tothe head base surface 124 and generally faces opposite the cutting headdirection of rotation R. A cap recess forward surface 154 adjacent thehead torque transmission wall 152 is generally parallel to the head basesurface 124.

In the embodiment seen in FIGS. 2A, 4A and 5A, however, cutting head100A is devoid of coolant channels. In this instance, in a top view ofthe cutting head 100A, the head surface 122A extends circumferentiallyin an uninterrupted manner from a first head flute 139A to a cuttingedge 142A formed adjacent a second head flute 139B (see FIG. 4A).Similarly, on the underside of the cutting head 100A, the cap recesssurface 154A extends circumferentially in an uninterrupted manner fromthe torque transmission wall 152A adjacent the first component head basesurface 146A, to the second component head base surface 148A (see FIG.5A).

The cross-sectional view of FIG. 6 is taken along a line that passesthrough the cutting head longitudinal axis L, opposing protrusions 110B,110D, opposing head fixation surfaces 128B, 128D, and opposing notches130B, 130D. As seen in FIG. 6, a separation W1 at the deepest portion ofthe opposing notches is less than a separation W2 of the opposing headfixation surfaces 128B, 128D, which in turn is less than a separation W3of the opposing protrusions 110B, 110D at the radial surfaces 135, orW1<W2<W3. Therefore, each notch has a deepest portion that is radiallyinward of an adjacent head fixation surface, and the protrusions definea maximum dimension W3 of the fixation portion in a directionperpendicular to the cutting head longitudinal axis L. In oneembodiment, this maximum dimension W3 is found between the radiallydirected protrusion surfaces 135 of opposing protrusions.

As seen in FIG. 7, the tool shank 200 has a shank longitudinal axis S.At a forward end thereof, the tool shank 200 has two diametricallydisposed shank coupling portions 256A, 256B each peripherally bound by ashank peripheral surface 258 and two shank flutes 260A, 260B. Each shankcoupling portion 256A, 256B has a forwardly facing shank support surface262 extending from the shank peripheral surface 258 generallytransversely inwardly to a shank pocket recess 264 formed between theshank coupling portions 256A, 256B.

Within the shank pocket recess 264 is a concave rear recess surface 270(see FIG. 8). At the base of an inner surface of each shank couplingportion 256A, 256B, the concave rear recess surface 270 connects at itsouter edges to an arcuate recess relief wall 267. The recess relief wall267, in turn, connects to a rearwardly facing recess retaining surface269. The inner surface of each shank coupling portion 256A, 256B furthercomprises a leading shank fixation surface 288 and a trailing shankfixation surface 290, the two shank fixation surfaces 288, 290 beingseparated by a vertically extending shank fixation recess 286 whichcommunicates with the recess relief wall 267.

Each shank fixation surface 288, 290 is parallel to the shanklongitudinal axis S. In one embodiment, each shank fixation surface 288,290 has an extent along the shank longitudinal axis S that is greaterthan an extent in a direction transverse to the shank longitudinal axisS. Thus, in one embodiment, each shank fixation surface 288, 290 forms arectangular surface. In some embodiments, each shank fixation surface288, 290 has an arcuate shape in a cross-section taken perpendicular tothe shank longitudinal axis S (see FIG. 11), and thus comprises aportion of a cylindrical shell. The shape of the shank pocket recess 264is such that a narrow neck region is formed in each shank couplingportion 256A, 256B adjacent the join between the shank fixation surface288, 290 and the rear recess surface 270. The narrow neck region makesthe shank coupling portions 256A, 256B resiliently displaceable.

A protuberance 274 protrudes forwardly from each shank support surface262 and a depression 279 is formed in each shank support surface 262 ata trailing end of the protuberance 274. The protuberance 274 and thedepression 279 divide the shank support surface 262 into a first,leading component shank support surface 276 at a leading end and asecond, trailing component shank support surface 278 at a trailing endthereof.

In some embodiments, the shank has at least two shank coolant channels280, with at least one shank coolant channel 280 emerging from eachshank coupling portion 256A, 256B. Each shank coolant channel 280 opensout into a surface of the depression 279 where it can communicate withthe head coolant channel 150. In one embodiment, the shank coolantchannel 280 opens out at a point between the first and second componentshank support surfaces 276, 278, and more specifically, between theprotuberance 274 and the second component shank support surface 278.

In the embodiment seen in FIG. 7A, however, the tool shank 200A isdevoid of coolant channels. In this instance, a slight depression 279Amay still be present between the second component shank support surface278A and the protuberance 274A (see FIG. 7). This slight depression 279Acan facilitate mounting the cutting head 100A onto the shank 200A, asdiscussed further below.

A shank torque transmission wall 282 adjacent the first component shanksupport surface 276 extends along a portion of the protuberance 274. Theshank torque transmission wall 282 is transverse to the shank supportsurface 262 and generally faces the direction of rotation. Aprotuberance forward surface 284 merges with the shank torquetransmission wall 282 via a beveled transition surface 283, and isgenerally parallel to the shank support surface 262. A shank fixationrecess 286 separates the first, leading shank fixation surface 288formed at a leading end of the shank coupling portion 256A, 256B fromthe second, trailing shank fixation surface 290 formed at a trailing endof the shank coupling portion 256A, 256B.

With reference to FIG. 8, in order to mount the cutting head 100 on thetool shank 200, the cutting head 100 and tool shank 200 are axiallyaligned so that the cutting head segments 140A, 140B and shank couplingportions 256A, 256B are arranged in opposing pairs. For each pair, thecap recess 144 is principally above a portion of the protuberance 274,the head fixation recess 132A, 132B is above the first shank fixationsurface 288, the second protrusion 128B, 128D is above the shankfixation recess 286, and the second component head base surface 148 isabove the depression 279.

With reference to FIG. 9, the cutting head 100 and tool shank 200 arethen urged towards each other so that the cap recess 144 at leastpartially receives the protuberance 274, the head fixation recess 132A,132B opposes the first shank fixation surface 288, the second protrusion128B, 128D is inserted into the shank fixation recess 286, and thesecond component head base surface 148 is received into the depression279.

Finally, the cutting head 100 is brought into a fully mounted position(FIG. 10) by rotating it in the direction indicated by rotational arrowP (FIG. 9) relative to the tool shank 200 until the head and shanktorque transmission walls 152, 282 abut. As the cutting head 100 isrotated relative to the tool shank 200, the second component head basesurface 148 moves out of the depression 279 and onto the secondcomponent shank support surface 278.

As the cutting head is rotated, the head coolant channel 150 becomesaligned with the shank coolant channel 280, thereby permitting coolantflow through the shank and cutting head during operation. However, asseen in FIGS. 8A and 9A, even when the coolant channels are absent, thesecond component head base surface 148A still initially starts above thedepression 279A, and then again enters the depression 279A. Also, as thecutting head 110A is rotated, the second component head base surface148A moves out of the depression 279A and onto the second componentshank support surface 278A.

In addition, the fixation portion 120 of the cutting head 100 contactsand displaces the resilient shank coupling portions 256A, 256B in aradially outward direction as the head fixation surfaces and the shankfixation surfaces come into abutment with one another. Moreparticularly, in the fully mounted position, the leading head fixationsurfaces 128A, 128C abut the first shank fixation surface 288 formed oneach shank coupling portion 256A, 256B, and the trailing head fixationsurfaces 128B, 128D abut the second shank fixation surface 288 formed oneach shank coupling portion 256A, 256B (as seen in FIG. 11). Because allthe head fixation surfaces 128A, 128B, 128C, 128D are generally parallelto the longitudinal axis L of the cutting head 100 and all the shankfixation surfaces 288, 290 are parallel to the longitudinal axis S ofthe tool shank 200, virtually the entire force exerted by each headfixation surface against its corresponding shank fixation surface isdirected in a radially outward direction relative to the longitudinaltool axis X. This contrasts with the angled force applied between thesloped head fixation surfaces and the sloped shank fixation surfaces inthe aforementioned U.S. Published Patent Application No. 2005/0260046A1. And unlike in this prior art reference, when the head fixationsurfaces 128A, 128B, 128C, 128D abut the shank fixation surfaces 288,290, the entire bulge 108 is spaced apart from walls of shank pocketrecess 264.

It should be noted, however, that in the fully mounted position, thecutting head's rounded bottom 109 and the rear recess surface 270 arenot in abutment so that a gap G1 exists between them (FIG. 10). Thisspace is preferably small so that chips cut from a workpiece will notbecome lodged in the space. A gap G2 also exits between the radiallydirected protrusion surface 135 of each protrusion and the recess reliefwall 267 formed in the shank pocket recess 264. Furthermore, yet anothergap G3 exists between the beveled protrusion surface 133 of eachprotrusion and the rearwardly facing recess retaining surface 269. As aconsequence, in one embodiment, the protrusions are unabutted bysurfaces of the shank pocket recess 264, during normal operation of thetool. Preferably, the entire bulge 108 remains unabutted by surfaces ofthe shank pocket recess 264, including the rearwardly facing recessretaining surface 269, in the fully mounted position and while the drillis being operated.

During a drilling operation, the forwardmost tip of the cutting head 100enters the workpiece and forms a hole therein. Due to the high heat andcutting forces involved, it often becomes difficult to withdraw the toolfrom the workpiece. On occasion, as the tool is withdrawn, the cuttinghead 100 begins to pull out from the frictional grasp of the shankfixation surfaces 288, 290. In such instances, after the cutting head100 has slightly pulled out, the gap G3 closes as the beveled protrusionsurface 133 on the upper surface of the bulge abuts the rearwardlyfacing recess retaining surface 269, thereby preventing the cutting head100 from fully pulling out of the shank pocket recess 264. As can beseen in FIG. 10, the pullout prevention property (of the cutting head100 from shank pocket recess 264) may also be considered as a result ofthe fact that the bulge 108 has a transverse maximum dimension(perpendicular to the cutting head longitudinal axis L) which is greaterthan a transverse maximum dimension of the stem 106. This can also beexpressed by the relation W3>W2 as shown in FIG. 6. Since the fixationsurfaces 128A, 128B, 128C, 128D of the stem 106 abut the shank fixationsurfaces 288, 290, the region of the shank fixation recess 286 in whichthe stem 106 is located also has a transverse maximum dimension (whichequals W2) which is smaller than the transverse maximum dimension of thebulge 108, therefore preventing passage of the bulge 108 through theregion of the shank fixation recess 286 in which the stem 106 islocated. In other words, due to the relatively large dimension of thebulge 108, the cutting head 100 cannot be axially displaced by adistance greater than approximately the dimension of the gap G3. Thispullout prevention property holds for all the embodiments describedherein.

In the fully mounted position (FIG. 10), the cutting head 100 isretained in a self clamping manner by the tool shank 200. Accordingly,the cutting head 100 can be releasably mounted to the shank 200 withoutthe use of one or more screws. For each of the opposing pairs of headsegments 140A, 140B and shank coupling portions 256A, 256B, in additionto the abutment of the head and shank torque transmission walls 152,282, the first component head base surface 146 and first component shanksupport surface 276 abut, and the second component head base surface 148and second component shank support surface 278 abut. However, there is agap G4 between the protuberance forward surface 284 and the cap recessforward surface 154. Thus, the cutting head 100 is axially supported bythe tool shank 200 at four spaced apart axial support regions on theshank support surfaces 262, formed by the abutment of the first andsecond component head base surfaces 146, 148 with the first and secondcomponent shank support surfaces 276, 278; respectively, of each of theopposing pairs of head segments 140A, 140B and shank coupling portions256A, 256B. With four spaced apart axial support regions the cuttinghead 100 is stably coupled to the tool shank 200.

Furthermore, each shank support surface 262 is preferably flat and thetwo component shank support surfaces 276, 278 are preferably coplanar.Similarly, each head base surface 124 is preferably flat and the twocomponent head base surfaces 146, 148 are preferably coplanar. Flat andcoplanar axial support surfaces are advantageous over non-coplanar axialsupport surfaces since it is easier to achieve the required tolerancesfor coplanar surfaces than it is for non-coplanar surfaces.

One of the advantages of having the entire bulge 108 unabutted bysurfaces of the shank pocket recess 264 in the fully mounted position isthe ease of manufacture. Since, in the fully mounted position the firstcomponent head base surface 146 and first component shank supportsurface 276 abut, and the second component head base surface 148 andsecond component shank support surface 278 abut, a requirement ofabutment between the bulge 108 and surfaces of the shank pocket recess264 would necessitate manufacturing the cutting head 100 with veryprecise axial distances between the bulge 108 and first and secondcomponent head base surfaces 146, 148 on the one hand and between thecorresponding abutted surfaces of the tool shank 200 on the other hand.

FIG. 12 shows a partial cross-sectional view of a tool 400 in accordancewith a second embodiment of the present invention. The cutting head 401of tool 400 has a cutting head longitudinal axis L2 and a bulge 402 thatis formed on a medial portion of the mounting stem 404. Each of the atleast two head fixation surfaces 406 (only one of which is shown) islocated between a corresponding protrusion 408 and the cap portion 410.The fixation portion 412 further comprises at least two additional headfixation surfaces 414 (only one of which is shown). The additional headfixation surfaces 414 are located between the protrusions 408 and alower end 416 of the mounting stem 404. Each of the at least twoadditional head fixation surfaces is also parallel to the cutting headlongitudinal axis L2 and collinear with a corresponding head fixationsurface 406 that is located between the protrusions 408 and the capportion 410. In the tool 400, there is a first gap between the lower end416 of the mounting stem 404 and the rear recess surface 418, and asecond gap G5 also between the protrusion 408 and the clamping portionof the tool shank.

FIG. 13 is a cross-sectional view of a tool 420 in accordance with athird embodiment of the present invention. The cutting head 421 of tool420 has a cutting head longitudinal axis L3 and a bulge 422 formed on alower end of the mounting stem 424. Each head fixation surface 426 islocated between a corresponding protrusion 428 and the cap portion 430.Each protrusion 428 is provided with a radially outwardly directedprotrusion surface 425 which forms the upper surface of the protrusion428 and extends in a direction perpendicular to the cutting headlongitudinal axis L3. Each protrusion 428 is further provided with abeveled protrusion surface 427 which forms the lower surface of theprotrusion 428 and connects to the radially outwardly directedprotrusion surface 425 at a radially outermost apex 429. The beveledprotrusion surface 427 extends from a radially outward position to aradially inward position, in a rearward direction of the cutting head421.

FIG. 14 is a cross-sectional view of a tool 450 in accordance with afourth embodiment of the present invention. The cutting head 451 of tool450 has a cutting head longitudinal axis L4 and a bulge 452 formed on alower end of the mounting stem 454. Each head fixation surface 456 islocated between a corresponding protrusion 458 and the cap portion 460.Each protrusion 456 is provided with a first beveled protrusion surface455 that forms the upper surface of the protrusion 458. The firstbeveled protrusion surface 455 extends from a radially inward positionto a radially outward position, in a rearward direction of the cuttinghead 451. Each protrusion is further provided with a second beveledprotrusion surface 457 that forms the lower surface of the protrusion458 and connects to the first beveled protrusion surface 455 at aradially outermost apex 459. The second beveled protrusion surface 457extends from a radially outward position to a radially inward position,in a rearward direction of the cutting head 451.

FIG. 15 is a cross-sectional view of a tool 480 in accordance with afifth embodiment of the present invention. The cutting head 481 of tool480 has a cutting head longitudinal axis L5 and a bulge 482 formed on alower end of the mounting stem 484. Each head fixation surface 486 isformed on a radially outermost portion of a corresponding protrusion488. As a consequence, the bulge 488 takes up almost the entire extentof the fixation portion 499.

A sixth embodiment of the present invention is shown in FIGS. 16-18. Acutting head 600 has a cutting head axis L6, an operative direction ofrotation R, and comprises a cap portion 618 and a fixation portion 620.The cap portion 618 comprises a head top surface 622, a head basesurface 624 transverse to the cutting head axis L6 and a peripheral sidesurface 626 extending therebetween. The fixation portion 620 protrudesrearwardly from the head base surface 624 away from the head top surface622 and is substantially similar to the fixation portion 620 describedabove and comprises a mounting stem 606 similar to the mounting stem 106described above. In other embodiments, the fixation portion 620 may besubstantially similar to either of the fixation portions 412, 499described above.

Two head flutes 638A, 638B (not shown) extend generally axiallyrearwardly along a periphery of the cap portion 618 and fixation portion620, forming two identical head segments 640A, 640B therebetween. Eachhead segment 640A, 640B comprises a cutting edge 642 formed along anintersection of an adjacent rake surface 643 with the head surface 622.A head torque transmission wall 652 extends generally transverse to thehead base surface 624 and generally faces opposite the cutting headdirection of rotation R.

Some embodiments may have a head coolant channel (not shown) similar tothe head coolant channel 150 described above.

A tool shank 700 with a shank longitudinal axis S6 is also shown inFIGS. 16 to 18. At a forward end thereof, the tool shank 700 has twodiametrically disposed shank coupling portions 756A, 756B eachperipherally bound by a shank peripheral surface 758 and two shankflutes 760A, 760B. Each shank coupling portion 756A, 756B has aforwardly facing shank support surface 762 extending from the shankperipheral surface 758 generally transversely inwardly to a shank pocketrecess 764 formed between the shank coupling portions 756A, 756B. Theshank pocket recess 764 is substantially similar to the shank pocketrecess 264 described above.

A protuberance 774 protrudes forwardly from each shank support surface762 at a trailing end of each shank coupling portion 756A, 756B. In someembodiments there may be a depression formed in each shank supportsurface 262 at a leading end of the protuberance 774.

In some embodiments, the shank has two shank coolant channels similar tothe shank coolant channels 280 described above.

A shank torque transmission wall 782 extends along a portion of theprotuberance 774 and is transverse to the shank support surface 762 andgenerally faces the direction of rotation. A protuberance forwardsurface 784 merges with the shank torque transmission wall 782,optionally via a similar to the beveled transition surface 283 describedabove, and is generally parallel to the shank support surface 762.

With reference to FIGS. 17-18, in order to mount the cutting head 600 onthe tool shank 700, the cutting head 600 and tool shank 700 are axiallyaligned so that the cutting head segments 640A, 640B and shank flutes760A, 760B are arranged in opposing pairs. The cutting head 600 and toolshank 700 are then urged towards each other so that the shank pocketrecess 764 receives the fixation portion 620.

Finally, the cutting head 600 is brought into a fully mounted positionby rotating it in the direction indicated by rotational arrow P6relative to the tool shank 700 until the head and shank torquetransmission walls (652, 782 respectively) abut.

According to some embodiments, the head fixation surfaces of themounting stem of the fixation portion of the cutting head comprise aportion of either an elliptical or a circular cross section while eachof the fixation surfaces of the shank coupling portions comprises aportion of either a circular or an elliptical cross sectionrespectively.

According to some embodiments, as shown in FIGS. 19A-19C, end portions886 of the shank fixation surfaces 888 of the shank coupling portions856 adjacent the shank flutes 860 are chamfered, so that initial contactbetween the head fixation surfaces 810 of the mounting stem 808 and theshank fixation surfaces 888 is not at the end portions 886 of the shankfixation surfaces 888 but rather closer to a central portion 889 of eachshank fixation surface 888. In a fully mounted position, abutmentbetween the shank fixation surfaces 888 and the head fixation surfaces810 is over an abutting region 890 of the fixation surface 888 whichextends from the central portion 889 of each shank fixation surface 888to the vicinity of the chamfered end portions 886, but excluding thechamfered end portions 886, so that leading and trailing gaps G8 areformed between the head fixation surfaces 810 and the shank fixationsurfaces 888 adjacent the shank flutes 860. Such an arrangement isadvantageous since if initial contact between the head fixation surfaces810 of the mounting stem 808 and the shank fixation surfaces 888 was totake place at the end portions 886 of the shank fixation surfaces 888,the latter could be damaged, since the mounting stem 808 may be made ofa hard metal, such as tungsten carbide, whereas the shank couplingportions 856 may be made of steel.

In the embodiments described with respect to FIGS. 1-11, the cuttinghead 100 is shown to have two head flutes 138A, 138B which form twocutting head segments 140A, 140B therebetween. And the shank 200 isshown to have two shank flutes 260A, 260B which connect with the headflutes 138A, 138B in the assembled tool, and two shank coupling portions256A, 256B which mate with the underside of the two cutting headsegments 104. Furthermore, associated with each cutting head segment140A, 140B are two head fixation surfaces 128A, 128B or 128B, 128C,respectively; and associated with the inner surface of each shankcutting portion 256A, 256B are two shank fixation surfaces 288, 290.

It should be understood, however, that in other embodiments the numberof flutes/cutting head segments/shank coupling portions may be someother number, such as 1, 3, 4 or even more. Similarly, in otherembodiments, the number of head fixation surfaces/shank fixationsurfaces associated with each cutting head segment/shank couplingportion, may also be some other number. For example, when the cuttinghead is an insert for a gun drill, only a single flute, cutting head,and shank coupling portion may be provided. And in tools having shanksand cutting heads with large cross-sectional diameters, three or moreflutes, cutting heads and shank coupling portions may be required.

Although the present invention has been described to a certain degree ofparticularity, it should be understood that various alterations andmodifications could be made without departing from the scope of theinvention as hereinafter claimed.

What is claimed is:
 1. A metal cutting head having a cutting headlongitudinal axis (L) defining forward and rearward directions, themetal cutting head comprising: a cap portion comprising a plurality ofhead segments separated by at least first and second head flutes, eachhead segment comprising a rearwardly facing head base surface formed ata rearward end of the cap portion; and a fixation portion joined to thecap portion and extending in a rearward direction of the cutting head,the fixation portion comprising: a mounting stem connected to the capportion and a plurality of circumferentially spaced apart protrusions onthe mounting stem; wherein a plurality of spaced apart head fixationsurfaces are formed on the fixation portion, each head fixation surfacebeing parallel to the cutting head longitudinal axis and configured toapply a radially outward force when the metal cutting head is mounted;and wherein the circumferentially spaced apart protrusions are distinctfrom the spaced apart head fixation surfaces.
 2. The metal cutting headaccording to claim 1, wherein: the protrusions define a maximumdimension of the fixation portion in a direction perpendicular to thecutting head longitudinal axis.
 3. The metal cutting head according toclaim 1, wherein: each head fixation surface has an arcuate shape in across-section taken perpendicular to the cutting head longitudinal axis.4. The metal cutting head according to claim 1, wherein: the protrusionsare formed on a lower end of the mounting stem; and each protrusion isprovided with a beveled protrusion surface which forms a lower surfaceof the protrusion.
 5. The metal cutting head according to claim 4,wherein: the beveled protrusion surface extends from a radially outwardposition to a radially inward position, in a rearward direction of thecutting head.
 6. A metal cutting tool comprising: a metal cutting headreleasably mounted on a forward end of a tool shank, the metal cuttinghead and the tool shank having a common axis of rotation and a commondirection of rotation, wherein: the metal cutting head comprises: acutting head longitudinal axis (L) which is coincident with the commonaxis of rotation; a cap portion comprising a plurality of head segmentsseparated by at least first and second head flutes, each head segmentcomprising a rearwardly facing head base surface formed at a rearwardend of the cap portion; and a fixation portion joined to the cap portionand extending in a rearward direction of the cutting head, the fixationportion comprising: a mounting stem connected to the cap portion andplurality of circumferentially spaced apart protrusions on the mountingstem; wherein a plurality of spaced apart head fixation surfaces areformed on the fixation portion, each head fixation surface beingparallel to the cutting head longitudinal axis; and wherein thecircumferentially spaced apart protrusions are distinct from the spacedapart head fixation surfaces; and the tool shank comprises: a shanklongitudinal axis (S) which is coincident with the common axis ofrotation; a plurality of shank coupling portions, equal in number to theplurality of head segments, formed at the forward end of the tool shank,and a shank pocket recess formed between the shank coupling portions,each shank coupling portion including: a forwardly facing shank supportsurface; and an inner surface comprising a plurality shank fixationsurfaces, each shank fixation surface being parallel to the shanklongitudinal axis; wherein: the rearwardly facing head base surface ofeach head segment is supported by the forwardly facing shank supportsurface of a corresponding shank coupling portion; each head fixationsurface abuts an opposing shank fixation surface over an abutmentregion; the protrusions define a maximum dimension of the fixationportion in a direction perpendicular to the cutting head longitudinalaxis and the protrusions are spaced apart from walls of the shank pocketrecess.
 7. The metal cutting tool according to claim 6, wherein: thetool shank further comprises: a protuberance protruding forwardly fromeach shank support surface, the protuberance having a protuberanceforward surface; and a shank torque transmission wall extending along aportion of the protuberance transverse to the shank support surface andgenerally facing the direction of rotation; the cutting head furthercomprises: at least one circumferentially facing head torquetransmission wall extending generally transversely to the head basesurface and generally facing opposite the direction of rotation; and theshank torque transmission wall abuts the head torque transmission wall.8. The metal cutting tool according to claim 7, wherein: theprotuberance forward surface is generally parallel to the shank supportsurface.
 9. The metal cutting tool according to claim 6, wherein: theplurality of circumferentially spaced apart protrusions are formed on alower end of the mounting stem.
 10. The metal cutting tool according toclaim 6, wherein: the tool shank further comprises at least first andsecond shank flutes; the head flutes and the shank flutes are generallyaligned; and adjacent the shank flutes there is a gap between the headand shank fixation surfaces of opposing pairs of head and shank fixationsurfaces.
 11. A metal cutting head having a cutting head longitudinalaxis (L) defining forward and rearward directions, the metal cuttinghead comprising: a cap portion comprising a plurality of head segmentsseparated by at least first and second head flutes, each head segmentcomprising a rearwardly facing head base surface formed at a rearwardend of the cap portion; and a fixation portion joined to the cap portionand extending in a rearward direction of the cutting head, the fixationportion comprising: a mounting stem connected to the cap portion and aplurality of circumferentially spaced apart protrusions on the mountingstem; wherein a plurality of spaced apart head fixation surfaces areformed on the fixation portion, each head fixation surface beingparallel to the cutting head longitudinal axis and configured such that,in any cross-section taken perpendicular to the longitudinal axis andpassing through the head fixation surfaces, the head fixation surfacesare the radially outermost surfaces; and wherein the circumferentiallyspaced apart protrusions are distinct from the spaced apart headfixation surfaces.
 12. The metal cutting head according to claim 11,wherein: the protrusions define a maximum dimension of the fixationportion in a direction perpendicular to the cutting head longitudinalaxis.
 13. The metal cutting head according to claim 11, wherein: eachhead fixation surface has an arcuate shape in a cross-section takenperpendicular to the cutting head longitudinal axis.
 14. The metalcutting head according to claim 11, wherein: the protrusions are formedon a lower end of the mounting stem; and each protrusion is providedwith a beveled protrusion surface which forms a lower surface of theprotrusion.
 15. The metal cutting head according to claim 14, wherein:the beveled protrusion surface extends from a radially outward positionto a radially inward position, in a rearward direction of the cuttinghead.
 16. The metal cutting head according to claim 11, wherein: thebeveled protrusion surface extends from a radially outward position to aradially inward position, in a rearward direction of the cutting head.